Generally, a cover glass is mounted to a front end of an insertion portion (scope portion) of an endoscope apparatus, and an image of the inside of a body cavity is obtained through the cover glass. When the insertion portion of the endoscope apparatus is inserted into the body cavity, condensation may cause fogging of the cover glass. The fogging of the cover glass prevents a satisfactory image of the inside of the body cavity from being obtained. However, if the insertion portion is withdrawn from the body cavity to defog the cover glass during surgery, surgery efficiency is reduced.
Thus, a conventional endoscope apparatus has been known having a function of defogging a cover glass with an insertion portion being inserted into a body cavity during surgery. In the conventional endoscope apparatus, an ultrasound transducer is provided near the cover glass at a front end of the insertion portion, and the ultrasound transducer provides ultrasound vibration to the cover glass to defog the cover glass. For example, Japanese Patent Laid-Open No. 2006-55275 discloses such an endoscope apparatus.
However, the conventional endoscope apparatus requires space for providing the ultrasound transducer at the front end of the insertion portion, thereby preventing a reduction in size of the insertion portion. For providing the ultrasound transducer at the front end of the insertion portion, a wire needs to be passed through the insertion portion to supply or control electric power. However, this requires measures to prevent leakage of electricity from the insertion portion in the body cavity, thereby increasing the cost and size of the insertion portion of the endoscope apparatus. The ultrasound transducer generates relatively weak vibration, and even if the ultrasound transducer is placed near the cover glass, an insufficient defogging effect of the cover glass is sometimes obtained.
Also, the insertion portion of the conventional endoscope apparatus is a so-called exclusive component into which the ultrasound transducer is incorporated. Thus, for example, an endoscope apparatus including a replaceable insertion portion according to the condition or purpose of use sometimes includes an exclusive insertion portion having a defogging function and also a general insertion portion having no defogging function. In such a case, the exclusive insertion portion sometimes needs to be selected due to the need for the defogging function, though the general insertion portion should be selected according to the condition of use. In this manner, the conventional endoscope apparatus has low flexibility in selection of the insertion portion of the endoscope apparatus.